1. Field of the Invention
The present invention relates to an elastic wave resonator including multiple divided resonators that are divided in series and a ladder filter including the elastic wave resonator.
2. Description of the Related Art
Elastic wave filters each including multiple elastic wave resonators have hitherto been widely used in, for example, bandpass filters in cellular phones.
Japanese Unexamined Patent Application Publication No. 57-119509 discloses an elastic wave resonator composing such an elastic wave filter. In Japanese Unexamined Patent Application Publication No. 57-119509, an interdigital transducer (IDT) electrode defining the elastic wave resonator is divided in series in a direction in which electrode fingers extend.
Japanese Unexamined Patent Application Publication No. 2003-324335 discloses a ladder filter including multiple elastic wave resonators. In Japanese Unexamined Patent Application Publication No. 200-324335, a configuration is described in which dummy electrode fingers are provided in an IDT electrode that is not divided in series.
In the elastic wave resonator including the IDT electrode that is divided in series, as in Japanese Unexamined Patent Application Publication No. 57-119509, the electric power handling capability is improved. However, the loss is likely to increase if elastic waves leak out from the resonator.
When the dummy electrode fingers are provided in the IDT electrode, as in Japanese Unexamined Patent Application Publication No. 2003-324335, leakage of the elastic waves is capable of being suppressed. However, when the dummy electrode fingers described in Japanese Unexamined Patent Application Publication No. 2003-324335 are provided in the IDT electrode that is divided in series, described in Japanese Unexamined Patent Application Publication No. 57-119509, it is difficult to reduce the size.